The proposed research in experimental animals is designed to evaluate alternatives to total splenectomy (including circulatory control, partial splenectomy, omental autotransplantation, and chemical splenectomy) by determining the relationship of splenic mass to hematologic and immune function. Growth potential, the peripheral blood cell picture, the course and surfival after intravenous virulent pneumococcal challenge with and without prior complement depletion, and antibody response to intravenous particulate antigen will be examined after removal, reduction, and augumentation of splenic mass in rats and mice by a variety of methods. The findings and mathematic models derived should help to guide the development of therapeutic alternatives to total splenectomy which preserve protective function of the spleen in trauma and hypersplenism yet prevent recurrence of the hematologic disturbance in the latter syndrome.